Hi Martin,
Just saw your post and as I was cleaning my pv and exhaust today I took note of that breather you have in the first picture. I have one in the spot you have it and I also have another for dribble coming out of the powervalve.
However I did see that these are different to each other on my bike. The one coming out of the powervalve is hollow, the one coming from the exhaust that you mention is definitely not hollow. When I had a close look at it, it does have a hole in it about the size of a pin.
I'm not sure of what the consequence of drilling this out would be for you and someone else may be able to elaborate more but I'm guessing there is a reason for this. Possibly to lower the chance of water or other foreign bodies entering the exhaust port n cylinder.
Regards
Josh